I have a feeling that this will become a stupid question. But I haven't found the answer yet so what ever.
I have made a 4 operator FM patch. When put it inside the [poly~], it can only produce one sound at any given moment.
I suspect it's due to that I use [send~] and [receive~] in the [4opFMsub] subpatch (They are strictly inside the subpatch). However, from what I searched in the form, the problem should be solved in Max 6.0.4 (I use 6.0.7). Also I tried the same patch in Max 5 and the result is the same.
I attached the whole patch. You can load sound preset by click the read button inside the [4opFMsub] patch, and load either json file in the patches/ folder.
Thanks for any suggestion.